The present invention relates in general to methods of preparing bakery doughs and to containers for packaging prepared refrigerated doughs. In particular, it relates to a method of proofing dough adapted for refrigerated storage, an improved container for refrigerated doughs, and a method for forming a dough product utilizing the improved container.
The manufacture of doughs suitable for refrigerated storage and for cooking at a later date is well known. One problem inherent in known refrigerated dough products is that the shelf life of existing products is limited. The dough products are known to degrade over time and lose textural properties. The bacteria levels also increase over time, causing the product to become discolored and spoiled. Exposure of the dough to oxygen over time also causes discoloration and spoilage of the dough. The liquid components of the dough are known to separate and a syrup forms which leaks out of known containers soiling the outer labels. The syrup leakage is particularly objectionable to consumers.
Examples of patents which disclose refrigerated dough compositions are Yong et al. U.S. Pat. No. 4,381,315, Matz U.S. Pat. Nos. 3,356,506 and 3,397,064, Atwell U.S. Pat. No. 4,526,801 and Lutz U.S. Pat. No. 3,669,682.
The Yong et al. U.S. Pat. No. 4,381,315 describes refrigerated dough compositions for forming products with bread-like characteristics and is herein incorporated by reference. During storage of these doughs, pressure within the container builds as a result of gasses generated by the leavening process. Yong discloses that preferred dough compositions for doughs stored under pressure contain between 28 and 36.5 percent by weight water and between 2 and 3.7 percent by weight leavening agents. The doughs are suitable for storing in a container having an internal pressure of between 1 and 25 p.s.i.g.
The Matz U.S. Pat. No. 3,356,506 patent is also representative of refrigerated dough compositions. Examples of dough compositions disclosed in the Matz '506 patent contain between about 2.8 percent and about 3.1 percent leavening by weight of the dough, and about 27 percent by weight water. The dough is placed in a container capable of venting gasses produced during proofing until the dough fills the volume of the can. At that point, the dough plugs the escape path of the gas, and the internal pressure of the container begins to rise.
The Matz U.S. Pat. No. 3,397,064 also discloses refrigerated dough compositions. The biscuit dough composition of Example 1 contains 2.1 percent leavener and 32.8 percent water, by weight. The dough compositions disclosed in the Matz 064' patent are also suitable for packaging and proofing in vented cans which seal when the dough expands to completely fill the volume of the container. Thereafter, the by-product gasses produced as a result of leavening increase the internal storage pressure within the container to between 8 and 16 p.s.i.g.
Atwell U.S. Pat. No. 4,526,801 discloses an improved refrigerated dough composition which when placed in a container generates preferred container pressures of between 2 and 7 p.s.i.g. at 40 degrees Fahrenheit. The disclosed formulations contain between 28 and 36.5 percent by weight water and between 2.0 and 3.7 percent by weight leaveners. The doughs also have as a component a volatilizable edible substance having a vaporization temperature of less than about 200 degrees Fahrenheit. The added component provides higher specific volume upon baking.
The Lutz U.S. Pat. No. 3,669,682 patent discloses a refrigerated dough composition which is resistant to crystalline growth during storage. Dough formulations commonly include a combination of a slow acting leavening acid and an alkaline substance capable of releasing carbon dioxide upon reaction with the leavening acid. The most common system includes sodium acid pyrophosphate and sodium bicarbonate. These leaveners tend to react in the aqueous phase of the dough, forming visible disodium orthophosphate dodecahydrate crystals. This crystal formation most frequently occurs at storage temperatures of from 32 to 50 degrees Fahrenheit. The Lutz patent sought to eliminate the problem of crystal formation by introducing a polyphosphate having an average chain length from about 4 to about 8 to the dough composition.
Dough compositions as the ones discussed above can be either proofed before or after packaging. "Proofing" for purposes of this disclosure is defined as a preliminary heating step in which the dough is at ambient pressure, in which the leavening agents react, expanding the dough by approximately 1 to about 15 percent. After proofing, the dough is further developed by storage in a sealed container at refrigeration temperatures until a point in which the internal pressure of the container has reached a selected equilibrium pressure, and when the dough has reached an equilibrium temperature. During the "developing step" the dough changes in quality including for example texture, density, flavor and crumb consistency.
Proofing of refrigerated doughs is typically accomplished by first packaging the dough in a container which allows gas to escape until the dough expands to a volume sufficient to completely fill the container. The dough is packaged to fill between about 85 and about 99 percent of the available volume, and is then covered with a lid capable of venting gasses. The filled containers are exposed to temperatures ranging from about 70 to about 100 degrees Fahrenheit for a period of about 1 to about 3 hours. By elevating the temperature above ambient temperature, the leaveners act more quickly than if the dough remains at room temperature and at atmospheric pressure.
After the dough has filled the container, proofing is complete. Next, the dough is developed by placing the containers in refrigerated storage for a time sufficient for the internal pressure in the container to build and continue to rise until reaching a target equilibrium pressure of about 18 to about 20 p.s.i.g.
Pressure equilibrium is typically established in between about 8 and about 35 hours, bringing the total amount of time required for processing a prepared refrigerated dough up to between about 9 and about 48 hours. It is not until the above-described proofing and developing steps are complete that the dough can be baked and transformed into a baked good having acceptable quality including the proper texture, taste and density, for example.
There are several disadvantages to raising the temperature of the dough during proofing. Raising the temperature of the dough encourages the growth of microorganisms. Raising the temperature of the dough also requires the use of energy. Heating the dough and maintaining the elevated temperatures takes a great deal of time. Typically, proofing and developing together require from between about 9 and about 48 hours, depending on factors such as the type of product, the proofing temperature, the humidity, and whether the dough is in a container.
Although dough can be proofed before packaging, a common practice in forming refrigerated dough as described in Tucker et al. U.S. Pat. No. 3,897,563 includes placing the dough in a package such as a spiral wound composite can, capping the ends with caps capable of venting gasses, and placing the containers in a proofing chamber. The exposure time to heat is typically between about one and three hours, at 70 to 100 degrees Fahrenheit, depending upon many factors such as the size and shape of the dough and container, and the selected proofing temperature, for example. When the volume of the dough fills the container, proofing may be discontinued. After proofing, the packaged dough is "developed" by cooling to refrigeration temperatures and storing the product until the internal pressure of the dough container reaches equilibrium. What is meant by "developed" dough for purposes of this disclosure is dough which undergoes a chemical change which alters characteristics of the dough such as structure, texture, taste and crumb characteristics, for example. To develop the dough, the proofed containers are placed in refrigerated storage for at least 8 additional hours to allow the leaveners in the dough to continue to act, until the leaveners reach an internal container equilibrium pressure of between about 18 and about 20 p.s.i.g.
One known method of accelerating proofing is to select a chemical leavening system for the dough which elevates the internal container pressure during proofing. Katz et al. U.S. Pat. No. 4,792,456 discloses a dough composition suitable for proofing which after heating and subsequent refrigerated storage results in an elevated container pressure of about 20 p.s.i.g. The chemical leavening agent employed in this dough composition includes a mixture of glucono-delta-lactone and baking soda.
One known spiral wound container construction useful in proofing as discussed in Tucker includes capped ends capable of allowing oxygen entrapped in the product and present in the headspace of the container prior to proofing and gasses generated during proofing to escape to the atmosphere until the dough expands and fully occupies the volume of the container. This type of prior art end cap design is illustrated in FIG. 1.
FIG. 1 shows a cross-sectional view of a known end cap construction used for forming containers capable of venting gas. The container wall 10 is multilayered (or composite) and is substantially cylindrical. The cap 12 has an inner lip 14 and an integrally formed outer lip 16 which is folded inwardly onto itself such that the outer lip 16 is reinforced. After capping the container wall 10, the portion of the wall located between the inner lip 14 and the outer lip 16 is compressed. This construction allows gasses to vent from within the container, but does not allow the dough composition to escape. When the dough expands and comes into contact with the end cap, the dough plugs the gas escape path, and pressure builds within the container.
Several container designs having the above-mentioned venting feature are constructed to withstand the internal pressure generated during developing. One such container is described in Culley et al. U.S. Pat. No. 3,510,050. The container body includes a composite, multilayer spiral wound cylindrical structure having substantially flat, circular end covers. The end covers are conventionally applied and seamed. Culley et al., Column 6, lines 34-35. The container has a core layer which is formed from a relatively stiff paper can-grade paperboard. The disclosed container is formed by known spiral winding methods. Adhesively bonded to the inner surface of the core layer is a thin membrane layer. Adhesively bonded to the exterior surfaces of the core layer is a label layer which also protects the core layer from damage due to exposure to high humidity environments, for example.
The core layer includes a helical, longitudinal butt joint. Tensile members are provided which are formed of a material which will burst upon application of concentrated force. The most preferred tensile members are longitudinal strips which are positioned over and straddle the butt joint on the inner and outer surfaces. The tensile strips are attached by means of a hot melt adhesive applied on either side and spaced apart from the butt joint. The butt joint itself is not adhesively bonded. When the outer surface of the container is struck against a rigid corner surface, the tensile strips rupture, and the butt joint separates. Upon grasping opposite ends of the can and twisting in opposing directions, the can opens allowing the pressure to be released and the product to escape from the side of the can.
Non-bonded helical butt joints are used in several other known package configurations designed to withstand internal pressure. Another example is shown in Reid U.S. Pat. No. 3,972,468. This patent discloses a composite container having a core layer including an unbonded helical butt joint, an inner impermeable layer adhesively bonded to the core layer, a reinforcing strip adhesively bonded to the outer surface of the core layer covering the butt joint, and an outer layer adhesively bonded to the reinforcing strip and core layer. The adhesive bond between the outer layer and reinforcing strip is stronger than the bond between the reinforcing strip and core layer. When the label is removed, the reinforcing strip remains adhered to the label. The butt joint then separates. Upon grasping opposite ends of the container and twisting in opposing directions, the dough is released from the container. The internal pressure within the container assists in rupturing the reinforced butt joint.
The ability of a helical longitudinal butt joint to separate in part depends on the placement of the helical longitudinal seam of the inner membrane layer. By placing the membrane seam close to the butt joint, the butt joint separates more easily. Beauchamp U.S. Pat. No. 4,241,834 discloses a quick-open refrigerated dough container. The helical seam of the inner layer is closely spaced from the butt joint. Thornhill et al. U.S. Pat. No. 3,981,433 also discloses an inner layer seam closely spaced to a butt joint in the core layer.
The use of a container which is not air-tight has certain disadvantages. One problem with such a container is that the openings create a path for oxygen exchange. Additional oxygen encourages the growth of microorganisms which cause the dough to become discolored and spoil prematurely. Refrigerated doughs stored in such breathable containers therefore have a shorter shelf life than what is theoretically possible of refrigerated doughs.
As the dough in a vented container ages, water and other soluble substances separate from the mixture forming a syrup. Because the containers are under a positive pressure during storage, this syrup can escape from between the end caps and container wall and drip onto the outer surface of the container. The presence of syrup on the outer surface of the can is unacceptable to consumers.
The problem of extending the shelf life of baked goods has been extensively studied. The Davis et al. U.S. Pat. No. 3,718,483 discloses a method of preparing storage-stable bakery products. Dough or batter may be placed in a metal can and hermetically sealed under a vacuum. Drawing a vacuum of at least about 19.9 inches of mercury (absolute) on the uncooked contents of the can facilitates leavening, and creates sufficient capacity for gas formation during cooking. The leavened product then is completely cooked in the hermetically sealed can and the can remains sealed until the product is consumed.
The Davis patent also discloses a dough composition adapted for vacuum packing and cooking in a hermetically sealed can. The water content of cake batters must be between 10 and 20 percent of the batter by weight. The water content of doughs must be about 35 percent by weight. The amount of leaveners present in the cake and bread formulations ranged from between 0.5 percent and 1.0 percent by weight.
Other methods of preserving dough-based products are known. Joulin U.S. Pat. No. 4,357,356 discloses a method of producing a bread product from dough including the step of partially baking the dough, packing the partially cooked dough in hermetically sealed packaging under a vacuum, and sterilizing the partially baked dough in the package.
In addition to vacuum packaging partially cooked products, it is also known to vacuum package products after pasteurization or sterilization. For example, it is known to vacuum package concentrated fruit juices after sterilization. One such process is disclosed in Sansbury U.S. Pat. No. 4,343,427.
The Sansbury '427 reference also describes a composite can adapted for packaging hot juice. The composite can includes a spiral wound core layer, an inner impervious layer and an outer label layer. The core layer is preferably formed from paperboard and includes a helical skive joint having adjacent faces which are adhesively bonded with a strongly adhering adhesive to prevent rupture of the can. A "skive joint" for purposes of this disclosure is a joint which is cut through the cylinder wall in a direction other than radially outward and substantially perpendicular to a point along a main cylindrical axis. The inner layer of the can structure is adhesively bonded to the inner surface of the core layer and has a helical seam which is spaced substantially apart from the skive joint to further strengthen the can. The thickness of the core layer is such that the can is capable of withstanding an internal vacuum caused by cooling of the hot liquid after the can is sealed. The container disclosed in Sansbury is hermetically sealed.